Revert "sandbox demo of shutdown cancel."

This reverts commit 851baa6537.

samples/Sandbox/App.axaml.cs

@@ -16,14 +16,7 @@ namespace Sandbox
             if (ApplicationLifetime is IClassicDesktopStyleApplicationLifetime desktopLifetime)
             {
                 desktopLifetime.MainWindow = new MainWindow();
-
-                desktopLifetime.ShutdownRequested += DesktopLifetime_ShutdownRequested;
             }
         }
-
-        private void DesktopLifetime_ShutdownRequested(object sender, System.ComponentModel.CancelEventArgs e)
-        {
-            e.Cancel = true;
-        }
     }
 }